1. Activity 1 Review the work from last lesson so that you can explain the following: -What is the purpose of a CPU. -What steps does the CPU take to process data. 5 minutes

2. The CPU Clock Speeds, The Cache and CPU Cores

3. The CPU – Central Processing Unit Review from Last Lesson (1) The CPU follows three steps in order to process data: It is known as the Fetch - Decode - Execute cycle (aka Fetch-Execute Cycle). Learning Objectives: iii) Explain how common characteristics of CPUs such as clock speed, cache size and number of cores affect their performance Understand how to correctly answer a range of exam questions 1) Fetch Data from Primary Storage (Main Memory / Ram) 2) Make Sense of the Data 3) Process the Data (perform calculations or logic comparisons)

4. The CPU – Central Processing Unit Review from Last Lesson (2) The three main parts of the CPU responsible for the F-D-E cycle are the: Control Unit Immediate Access Store (IAS) Arithmetic and Logic Unit (ALU) Learning Objectives: iii) Explain how common characteristics of CPUs such as clock speed, cache size and number of cores affect their performance Understand how to correctly answer a range of exam questions 1.An input device (e.g. keyboard) sends data to the CPU. The Control Unit receives this data. 2.The Control Unit sends this data into main memory to be used later. 3.When the time is right, the data will be transferred from main memory into cache (IAS) 4.The data will then be sent to the ALU for processing 5.The control unit will send the processed data back (for example to an output device such as a screen or monitor).

5. The CPU – Central Processing Unit Clock Speed The speed of the Fetch-Decode-Execute cycle is determined by the CPU’s clock chip. This chip uses a vibrating crystal that maintains a constant rate. The speed of the clock is measured in hertz (Hz) which is the amount of cycles per second. A clock speed of 500Hz means 500 cycles per second. Current computers have CPU clock speeds of 3GHz which means 3 Billion cycles per second. Learning Objectives: iii) Explain how common characteristics of CPUs such as clock speed, cache size and number of cores affect their performance Understand how to correctly answer a range of exam questions

6. Overclocking It is possible to increase the clock speed for a CPU. This is known as overclocking. In theory, if the clock is faster then the CPU can perform more calculations and perform faster. Problem is that CPUs get hot the more work they do – so overclocking is dangerous without the appropriate heat management.

7. The CPU – Central Processing Unit Primary and Secondary Storage A computer system will have two types of storage: -Primary – Cache, RAM (aka main memory), ROM -Secondary – Hard Disk, Flash Drive They differ in a number of ways: Learning Objectives: iii) Explain how common characteristics of CPUs such as clock speed, cache size and number of cores affect their performance Understand how to correctly answer a range of exam questions Primary StorageSecondary Storage Most Primary Storage is volatile (temporary). All secondary storage is (non- volatile) permanent Primary Storage is expensive and smaller. Secondary storage is usually cheaper and large Primary storage is smaller in capacity (L2 Cache is only 2MB) Secondary Storage is bigger in capacity Primary storage is closer to the CPU and/or is integrated onto it and therefore is faster. Secondary storage connects to the CPU via cables and therefore is slower

8. Speeds of data transfer of different devices Faster Slower

9. The CPU – Central Processing Unit The Cache As we have just seen CPUs can work very quickly indeed but unfortunately CPUs can only work when supplied with data. The RAM (that supplies the data) cannot work at the same speed. To overcome this the CPU’s cache memory will not just copy the instruction needed at that time, instead it will also copy the continuing instructions. Cache memory has read speeds similar to the CPU and is therefore much faster than RAM. So, to improve efficiency the CPU’s ‘Control Unit’ will look first in the cache for the next instruction to see if it has already been copied which reduces the time taken to access data. If the cache is larger, it is more likely that the next required instruction has already been transferred from the RAM to the CPU thus improving process time. Learning Objectives: iii) Explain how common characteristics of CPUs such as clock speed, cache size and number of cores affect their performance Understand how to correctly answer a range of exam questions 1 2 1. If data not in cache, request from RAM 2. Data (and future data) copied to cache for quicker access

10. Cache 1 2 1. If the required data is not in the cache, the control unit will request it from RAM 2. Data/Instructions (and future instructions) copied to cache for quicker access

11. The CPU – Central Processing Unit CPU Cores CPUs of today are pretty much at the limit of today’s technology. So if CPUs can’t go faster, the solution its to add 2 CPU chips, or 4, or 8, etc). These chips are called ‘ cores ’. Because the various cores can each carry out their own Fetch – Decode – Execute cycle it means that instructions can be processed at the same time. Allowing a CPU to process MORE data during the same time period. Learning Objectives: iii) Explain how common characteristics of CPUs such as clock speed, cache size and number of cores affect their performance Understand how to correctly answer a range of exam questions Dual Core processors have 2 CPU cores. Quad Core CPUs have 4 cores.

12. Exam Practice In a short while you will carry out some exam practice. But first… …Some exam technique tips.

13. Command Words What do each of these words mean? State/Identify/Give/Name Describe Describe/Explain/Discuss using examples Explain Discuss …you need to know because they appear in all exams. If (for example) the examiner asks you to EXPLAIN and you instead just DESCRIBE, you will not get any marks.

14. Command Words State/Identify/Give/Name Simply label a diagram, fill out a table or write a few words Describe Describing is ‘saying what you see’ E.G.: A computer will have a CPU, Primary and Secondary storage etc Explain Explaining is ‘saying why something is like that’ E.G.: A computer will have a CPU so that it can process all of the data the computer needs to perform a range of tasks. Primary and Secondary storage is needed because… Discuss Discussing is ‘looking at two sides of an issue, weighing up the two views and giving a conclusion’. Often these require a mini essay answer. E.G.: New technology could be seen as being bad for the environment because…, but on the other hand, new technology has lead to… In conclusion I believe that… Describe/Explain/Discuss using examples Finally, if you are asked to give examples in any of these types of questions – YOU MUST GIVE EXAMPLES!

15. Remember Whenever you answer exam questions you must CaM it! Look at the… Command words AND Marks Do what the question asks and make sure your answers have enough points or explanations to get the marks available.

16. Activity 2 Complete the timed exam practice questions. 5 minutes